1. Field of the invention
The present invention relates generally to slide fasteners, and more particularly to a fluid-tight (airtight and watertight) slide fastener suitable for wet suits, life preservers, etc.
2. Description of the Prior Art
U.S. Pat. No. 2,791,017, issued May 7, 1957 to F. Mulka, and U.S. Pat. No. 4,348,789, issued Sept. 14, 1982 to Brown, show a fluid-tight slide fastener of the type in which an inner longitudinal edge portion of each of opposed fluid-tight tapes is folded so as to extend around base portions of successive I-shaped coupling elements and in which successive C-shaped clamping strips surround, in clenched form, the folded edge portion over the base portion of the respective coupling element. The fluid-tight tape of the U.S. patent to Brown includes a textile fabric wholly covered with a fluid-tight layer of elastic rubber; the textile fabric serves to restrict the stretchability of the elastic rubber layer. The prior fluid-tight tape has the following problems:
If the fluid-tight tape is longitudinally stretchable, it is difficult to keep the coupling elements from staggering element-to-element distances or pitches during the coupling and uncoupling of the opposed stringers, thus impairing the function of the slide fastener.
If the fluid-tight tape is transversely non-stretchable, it cannot be deformed so as to follow the movement of the coupling elements during the coupling and uncoupling of the opposed stringers, thus causing not only non-smooth movement of a slider, but also inadequate fluid-tightness between the opposed stringers.